[chandler48]

IMO, you will be spending a lot of money for little return. You already have Durock on the walls which is an acceptable substrate for tile. Applying Kerdi won't gain anything. Yes your valve hole in the Durock is surgically too small. It should have come with a black spacer which would give you the proper dimension for the hole in the wall to where the trim will fit.

 

[chandler48]

This is my home, and I plan to live here for a long time.

Of course it is your choice to do what you feel best. We're here to give advice to questions asked. You need not worry about tile support around the valve. You will need to open the hole up more or the trim ring won't fit properly. I asked about the plastic trim ring template and protector. No answer on that yet. It should have been left in place to give you the proper opening at the valve. Red Gard or other sealants painted on the Durock will make the surface more waterproof, and cheaper than Schluter.

All I am trying to do is save you some money and achieve a good job at the same time. Best of luck with it.

 

[chandler48]

You're good to go. It appears the waffle side of the white ring gets the black seal, and goes against the tile, while the pretty gets put on last. You've taped your valve up to prevent thinset intervention. Just keep the area clean.